Reserves for Loss and Loss Expenses (Narrative) (Details) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Net of loss reserves discount | $ 33 | $ 28 |
| Increase in estimates for claims | 11 | 17 |
| Adjustment expense | 3 | 1 |
| Insurance | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Unfavorable reserve development net of premium offsets | 7 | 19 |
| Reinsurance & Monoline Excess | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Favorable reserve development net of premium offsets | $ 10 | $ 20 |